Air conditioning apparatus



w. H.- MACDONALD, JR .2,285,042

AIR CONDITIONING APPARATUS Jun l2, 1942.

Filed July 8, 1938 INVENTOIR M'laflUZMacdom@ J1! n BY 2RM,... Sig)ATTORNEY Patented June 2, 1942 2,285,042 AIR CONDITIONING APPARATUSWilliam H. Macdonald, Jr., Rochelle Park, N. r.,- assignor to CarrierCorporation, Syracuse, N. Y., a corporation of Delaware v ApplicationJuly -8., 1938, Serial No. 218,087

1 Claim.

This invention 'relates to air conditioning, and more particularly toair conditioning systems of the type employing refrigeration.

rThe general object of the invention is to provide an improved airconditioning system for controlling the temperature and moisture contentof air supplied to an enclosure for maintaining desired atmosphericconditions therein.

' Another object of the invention is to provideA an improved airconditioning system in which provision is m'ade for separatelycontrolling the temperature and the moisture content of air supp1ied`toa conditioned enclosure by contacting different portions of the air tobe conditioned with different heat exchange surfaces, the temperaturesof which surfaces are individually regulated to provide suchconditioning action that the different portions of the conditioned air,when intermingled subsequent to conditioning, will possessdesiredcharacteristics of temperature and humidity.

Otherv objects of the invention are to provide an improved airconditioning system which is adapted to control individually the drybulb temperature and moisture content of air supplied to a conditionedenclosure in a manner which is relatively simple, but which givesassurance that desired atmospheric conditions will be maintained in theconditioned enclosure at all times, regardless of variations in airconditioning load; which comprises relatively few elements and isrelatively inexpensive; and which is highly reliable in operation.

A feature of the invention resides in cooling va rst portion of an airstream in accordance 'with changes in humidity conditions in -saidenclosure, and supplying Aboth of said air stream portions to saidenclosure.

Another feature of the invention resides in passing. the air to beconditioned in contact with two or more heat exchange devices-arrangedin parallel with respect to the air ow thereover, so that differentportions of the air streamcontact with different heat exchange devices,utilizing at least one of the devices to regulate desirably the moisturecontent of the conditioned air, and utilizing at least another of thedevices tofregulate desirably the dry bulb temperature o'f theconditioned air. f

Another feature of the invention resides vin utilizing a. plurality ofdirect expansion heat exchange-devices 1oz-contact and heat exchangewith different portions of an air stream to be conditioned and suppliedto a conditioned area, and regulating the operation of said devices tocontrol the moisture -content and dry bulb temperature of air deliveredto the conditioned enclosure, said devices being arranged in parallelwith respect to the flow of refrigerant therethrough and being served bya common compressor apparatus.

Another feature of the invention resides in conditioning diierentlportions of an air stream ation of said devices being controlled byregulating the surface temperature of one or more of said devices inaccordance with 'changes in air conditioning load requirements.

Other objects, features and advantages of the invention will be moreclearly apparent from the following description, to be read inconnection lwith the accompanying drawing, in which:

Fig'. 1 diagrammatically represents an air conditioning system embodyingthe invention;

Figs. 2-4 diagrammatically represents modied forms of the invention; and

Fig; 5 diagrammatically represents a modifica-v tion of the inventionemploying secondary heat exchange, rather than direct expansion, forconditioning the treated air.

Referring to the drawing, numeral I0 designates an air conditioningcasing adapted to receive air from conditioned enclosure I I throughduct I2 and from the outdoor atmosphere through duct I3, the proportionsof return air and outvdoor air delivered to the casing being controlledby dampers I2a and I3a, in ducts I2 and I3,

respectively. While the airs delivered to the cased to discharge outdoorair through lower section lob of the vconditioner casing. If desired, apartition I4 separating the upper portion Illa 55 of the casing from thelower portion I0b thereof charge return air through the upper portionI'a v of the conditioner casing while duct I3 is adapt-l may be providedto give further assurance against the intermingling of returnzair andoutdoor air supplied to the conditioner casing. Fan I withdraws air fromboth portions of the conditioner casing I0 and supplies it to enclosurethrough supply duct I6.

In the upper portion Ia of the conditioner casing there is provided adirect expansion refrigerant evaporator I1 adapted to occupy the entirecross sectional area of the casing section Illa, so that allportionsofthe air4 stream passing through the section Illa are contacted with theevaporator I1. tion Illb of the conditioner casing there is providedevaporator I8 arranged to be contacted b y all portions of the airpassing through the conditioner casing portion |017. Liquid refrigerantis supplied to both evaporators through liquid supply line I9, theevaporators I1 and I8 being arranged in parallel with respect to liquid.supply line I9. Liquid refrigerant is supplied to the evaporator I1,under the control of expansion valve 20, the operation of which iscontrolled by thermal bulb or the like 22 at the outlet end ofevaporator I1 in a manner Well known in the art. Similarly, liquidrefrigerant is supplied to evaporator I8 under the control of expansionvalve 2|, regulated by thermal bulb or the like 22 located at the outletend of evaporator 8. nected in parallel to suction line 23 throughbranch connections 2 4V and 25 respectively. Evaporated refrigerantwithdrawn through suction line 2.3 is compressed by compressor 24 andcondensed in condenser 25a, of anysuitable type, and is then deliveredto receiver 26 for delivery to the evaporators.

The evaporator I1, serving the air withdrawn from the conditionedenclosure, is adapted primarily to effect the removal of sensible heatfrom the air contacting therewith. The evaporator I8, serving the airwithdrawn from the'outdoor atmosphere, is adapted to remove bothsensible heat and latent heat from the air contacting therewith, theprimary function of evaporator I8 being the removal of latent heat.A

In the branch connection 24 there is provided a. back pressureregulating valve 21 under the control of a dry bulb thermostat 28 whichmay be positioned in the return duct I2, as illustrated, or at any otherpoint where it may be subjected to the atmospheric dry bulb temperatureprevaillng in the conditioned enclosure I I. As the temperature aectingthe thermostat 28 rises, the ldegree of opening back pressure regulatingvalve Similarly, in the lower por- The evaporators I1 and I8 are con- Yevaporator I8 is so reduced, this evaporator provides increased coolingand dehumidifying effect. Conversely, when valve 21 is opened morewidely, to provide more cooling by evaporator I1, the pressure'andtemperature of evaporator I8 rise and hence there is less cooling anddehumidiiication by evaporator I8. In the embodiment of the inventionillustrated in Fig. 1, 'the dry bulb temperature of the conditionedenclosure is maintained within desired limits by the action ofthermostat 28, and while the relative humidity of the enclosure variessomewhat in this embodiment of the invention, this variation is within arange which is neither excessively great nor uncomfortable. y

If it is desired to maintain the' moisture con:` tent or relativehumidity of the conditioned enclosure within predetermined and closelimits, the arrangement of Fig. 2 may be utilized. In this modiiicationof the invention, the back pressure regulating valve 21 is eliminatedand aback pressure regulating valve 29 is provided at the outlet end ofevaporator I8 in branch connection 25. Valve 29 is under the control ofcontrol instrument 38 which maybe a wet bulb thermostat or hygrostat, asdesired, located at any desired point in the system, as in the returnduct I2. Employing this arrangement will maintain a wet bulb temperatureor relative humidity, according to the instrument employed, within closelimits While the dry bulb temperature within the conditioned enclosurewill vary somewhat. The operation of the embodiment illustrated in Fig.2 is essentially the same as that of the embodiment illustrated in Fig.1.

It is to be understood, of course, that in all embodiments of theinvention the sizes of the heat exchangers I1 and I8 are such that theheat exchanger I8 will have sufficient capacity to effect all requireddehumidication undermaximum load conditions and the heat exchanger I1will have suicient `capacity to effect all required sensible coolingunder maximum load conditions 21 is somewhat increased. 'I'he increasedopening of valve 21 causes a reduction of the pressure obtaining withinthe evaporator -I1 andv hence the evaporator operates at a somewhatreduced temperature to offset and correct'the increasing dry bulbtemperature affecting the thermostat 28. This operation continues untilthe thermostat is satised. Conversely, when the temperature affectingthermostatv 28 is too low, the valve 21 is closed somewhat, so that theevaporator I1 operates at a higher pressure and which is not eected byheat exchanger I8; By

sensible heat to total heat can be accommodated with no appreciablechange of temperature or relative humidity in the space conditioned, andthe system will be substantially self-balancing. Fig. 3 illustrates amodification of the invention which is identical with Fig. 1, exceptthat there is provided, in the branch connection 25 leading fromevaporator I8, an automatic pressure regulating valve 3|, of any desiredand wellknown type adapted to prevent the pressure in evaporator I8 fromfalling below a predetermined point. Thus while thermostat 28 and backpressure regulating valve 21 continue to provide close control of thedry bulb temperature, the pressure regulating valve 3| serves to preventexcessive sensible cooling and dehumidication by the evaporator I8during those intervals when the valve 21 is in relatively restrictedposition.

In substantially the same manner as pointed out in connection with Figs.1 and 2, the construction of Fig. 3 may be modied by providing in thebranch connection 25 a back pressure regulating. valve such as 29,suitably 'controlled by a hygrostat cr wet bulb thermostat such ascontrol instrument 30, such valve replacing the valve 3| in connection25. In such case, the valve 21 in branch connection 24 might be replacedby an automatic pressure 'regulating valve similar to valve 3|. Thusmodified, the arrangement of Fig. 3 would be operative to closelycontrol the wet bulb temperature or relative humidity of the conditionedenclosure and would prevent the temperature of the evaporator I1 fromfalling below a predetermined point.

The arrangement of Fig. 4 provides for the -closecontrol of both the drybulb temperature and the'relative humidity of the atmosphere of theconditioned enclosure, or of the dry bulb and wet bulb temperaturesthereof. As illustrated, back pressure regulating valve 21 in branchconnection 24 is under the control of dry bulb therwet bulb temperaturesor relative humidities in the conditioned enclosure.

Under normal operating conditions, refrigerant will flow through bothevaporators I1 and IB continuously, the refrigerant iiow being modulatedby the expansion valves and 2| and the back pressure regulating valvesprovided with one or both of the evaporators. However, the compressordriving means (not shown) may be provided with a well-known low pressurecut-out t so that the operation of the refrigerating system may beinterrupted when tbe pressure in the suction line 23 falls below apredetermined point. Further, it is to be understood that any' suitablemeans for variably regulating the capacity of the compressor inaccordance with variations in load requirements may be provided,

' 11,83'1, filed March 31, 1936, assigned-to applicants-assignee. f

As above set forth, the invention satisfactorily operates undervoperating conditions serving as the basis forthe design of the system.Occasionally, however, extreme and unusual operating conditions areencountered which' might tend to upset the balanced control of bothtemperature and relative humidity. Thus in the case of an extremely highlatent heat load, the dry bulb temperature of the airin the enclosuremight tend to drop below permissible limits, if it is attempted tomaintain t-he moisture content of the air in the enclosure within thenormal operating range. To meet such conditions, and to prevent theindoor dry bulb temperature from fall-` ing below a predeterminedminimum, applicant provides a relay control device 32 which is adaptedin well-known manner, when the dry bulb thermostat 28 is subjected to apredetermined low temperature, to prevent further opening of the valve29 byv hygrostat or, Wet bulb thermostat 39. It is to be understood thatany suitable stop means or the like may be utilized in conjunction withthe valve 29 for limiting the opening thereof when the dry bulbtemperature of the conditioned enclosure tends to become too low,without departing from the invention. For example, if the hygrostat 30variably controls the supply of compressed air tov valve'29, in the wellknown manner, for variably regulating the action the valve, then theremay bue provided in the co pressed air line leading to the hygrostat 30a device such as the C3 leak port cumulator,

manufactured by the Johnson Service Company,

which will reduce the amount of compressed air supplied to the hygrostatwhenever the dry bulby temperature affecting the thermostat falls belowa predetermined point, and thus serve to limit the opening of thesuction valve 29. Since this device, as well as various other forms ofapparatus capable of limiting and controlling the action of ahygrostatically controlled valve, in accordance with predeterminedvariations in temp-erature affecting a thermostat, are and have beenwell known in the art, per se, no further description thereof i s deemedrequired.

Fig. 5 illustrates a modification of the inventionin` which theconditioned air is treated by heat exchange with a, secondary heatexchange medium, rather than by direct expansion as in the embodimentsof the invention hereinabove described. In this form of the invention,there is provided a cooling coil 33 in the upper section Illa of theconditioner casing l0. The cooling coil 33 occupies substantially Atheentire cross sectional area of the casing section 10a, as described inconnection with evaporator I1 which it replaces and the function ofwhich it serves. Similarlyin the lower portion 10b of the conditionercasing I0 there is provided a cooling coil plained in connection withthe preceding gures.

A suitable conditioning -medium such as cold water or the like, issupplied to the coils 33 and 34 through supply line 35 and throughbranches 36 and 31 serving coils 33 and 34, respectively.

Branch connection 36 is provided with a threeway valve or the like, ofany desired construction, designated 38, which is adapted to vary theproportions 4of liquid received from supply line and from returnconnection 39 connected to the outlet end of coil 33. Valve 38 is underthe control. of dry bulbr thermostat 28a, which operates vin such mannerthat when additional sensible lcooling by the coil 433`is required, theamount of medium supplied to the coil from line 35 will be increased andthe amount of medium supplied through line 39 will be decreased. Whenthe thermostat 28a is subjected to a temperature which is lower thanthatdesired, the proportion of medium from line 35 is decreased and theproportion of medium from line 39 is increased.y A pump 40 deliverstothe coil 33 conditioning medium from the valve 38 i for circulationthrough the coil and for heat ex- 1 is required, and to decrease theproportion of medium drawnfrom line 35 and increasethe proportion ofmedium drawn from line 42 wheny less dehumidiiication is required. Pump43 delivers conditioning medium to the coil 34 from the valve 4I,for-circulation through the coil and for' heat .exchange with aircirculated in contact therewith. I

Conditioning medium which has been circube desirably regulated.

of the cooled conditioning medium for desirably i regulating theoperation of the refrigerating system in any desired manner, as byinterrupting the operation of the compressor whenever the medium in thetank 45 falls below a predetermined low temperature. Pump 53 drawscooled conditioning medium from the tank 45 and delivers it through line35, for use as above set forth.

In this embodiment of the invention, as in those above described, theconditioning of the air passed through the upper section of theconditioner casing is regulated to profyide desired control of the drybulb temperature in the conditioned enclosure and the coil 34 inthelower section of the conditioner casing is regulated so that themoisture content or relative humidity of the atmosphere of theconditioned enclosure -may It is to be understood that, if desired, thereturn lines 39 and 42 may be eliminated, and the three-wayvalvesreplaced by modulating valves of any suitable type, to providedesired regulation of the apparatus.

In the foregoing description, the evaporators I1 and I8 and the coils33'and 34 have each been described as constituting a single coil orexpansion device. It is to be understood, however, that any or all ofthese elements may comprise any number of component sections, arrangedeither iny series and/or in parallel with respect to 2,285,042 latedthrough' the coils 33 and 34 which isnot 34, have been illustrated asbeing arranged in vparallel with respect; to vair flow thereover, it isto be understood that any desired number of such heat exchange devicesmay be provided and controlled in accordance with the principles aboveset forth.

Since these and many other changes may be made in the invention' withoutdeparting from its scope, it is intended that all matter contained inthe above description or shown in the accompanying drawing shall beinterpreted as illustrative only and not in a limiting sense, applicantlimiting himself only as indicated in the appended claim.

I claim:

An air conditioning system of the character described including acasing, a first refrigerant evaporator positioned in said casing andoccupying one portion of a cross-sectional area thereof,v a secondrefrigerant evaporator positioned in said casing and occupying anotherportion of said cross-sectional area thereof, means for passing a streamof air through said casing whereby one portion of the air stream passesin cont'act with one of the evaporators and another portion of the airstream passes in contact with the other evaporator, means for supplyingliquid refrigerant to both of said evaporators, a refrigerantcompressor, a common suction connection from said evaporators leading(to said compressor, a back pressure regulating valve at the dischargeend of the one of the evaporators operative responsive to changes incondition of the air supplied to said evaporator to vary the pressure oftheA refrigerant in said evaporator, the arrangement of evaporatorsbeing such that the pressure of refrigerant in the other evaporator willsimultaneously be varied, an automatic pressure regulating valve at thedischarge end of the other evaportor to prevent the pressure in saidother evaporator from falling Abelow a predetermined point when thepressure in thefrst evaporatorI rises above a desired point, and meansfor mixing and delivering both portions of the air stream to anenclosure to be conditioned.

` WILLIAM H. MACDONALD, JR.

